JPH0440085A - Method of adjusting sampling phase for video printer - Google Patents

Abstract

PURPOSE:To enable sampling phase adjustment for a video printer, by which an adjusting operation can be realized easily by deciding the sampling timing of a luminance signal by using a general picture while a host device is operated. CONSTITUTION:A luminance data based on a picture signal V is fetched in a picture memory 5 by an initial sampling clock, and a picture element whose luminance difference from an adjacent picture data is maximum is extracted as a reference picture element from among the luminance data. Then, while the phase difference of the sampling clock corresponding to a horizontal synchronizing signal contained in the picture signal is changed, the luminance data is fetched in the picture memory 5. Then, the phase difference whose luminance difference of the reference picture element is maximum is decided as the appropriate phase difference of the sampling clock. Thus, it is possible to realize the sampling phase adjustment for the video printer by which the general display screen can easily be operated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for adjusting the sampling phase of a video printer that prints CRT display images, and particularly to a sampling phase adjustment method for a video printer that is easy to adjust. It is.

[Conventional technology]

Generally, when making a hard copy of a CRT display image, it is necessary to write the video signal to the image memory in the printer, but in order to accurately reproduce the screen pattern on the image memory, it is necessary to write the video signal accurately to the dots (pixels). Luminance data (video data) using a sampling clock compatible with
need to be written. For this reason, conventionally, the phase of the sampling clock generated from the PLL oscillator is appropriately delayed to optimally adjust the phase of the horizontal synchronization signal.

FIG. 4 is a block diagram schematically showing a general video printer device.

In the figure, (1) is a host device that outputs an image signal ■, and (2) is a CRT that displays an image based on the image signal ■.
, (3) is a video printer that takes in an image signal (2) and prints an image.

The image signal ■ is a Rusk scan method signal, and the luminance (
It is composed of a luminance signal A representing a video), a horizontal synchronizing signal BH for horizontal display line synchronization, and a vertical synchronizing signal BV representing the start of one screen.

Further, the video printer (3) is composed of the following (4) to (13).

(4) is an AD converter that converts analog brightness signal A into digital brightness data D, (5) is an image memory that stores brightness data D, and (6) is a converter that converts brightness data D in image memory (5). This is a printing unit that prints in image format.

(7) is a programmable delay circuit that generates a delayed signal R whose phase is delayed by a predetermined time from the horizontal synchronization signal BH;
) is a PLL oscillator that generates a sampling clock C that is synchronized with the delay signal R and has a frequency N times that of the horizontal synchronization signal;
(9) is the sampling clock C and the vertical synchronization signal BV
This is an input control unit that controls the storage operation of the image memory (5) based on the image memory (5). The sampling clock C is input to the AD converter (4) and controls the timing of AD converting the luminance signal A.

(10) is an MPU (microprocessor unit) that controls the overall operation of the video printer (3), and (11) is an MPU (microprocessor unit) that controls the overall operation of the video printer (3).
A ROM that stores the program of P U (10), (
12) is a nonvolatile memory consisting of E2FROM for storing various constants, etc., and (13) is an adjustment start button (13).
It is an operation panel having a). A printing section (6) to an input control section (9) and a ROM (11) to an operation panel (13) are connected to the MPU (10) via a bus.

FIG. 5 is an explanatory diagram showing the memory space of the image memory (5). n (n=1 to 400) is the horizontal line number, m (
m = 1 to 640) is a dot number (pixel number), and the image memory (5) consists of, for example, 400 lines x 640 dots.

Figure 6 shows the horizontal synchronizing signal BH, dot period, and brightness signal A.
3 is a waveform diagram showing the timing of the sampling clock C relative to the horizontal synchronizing signal BH, and ΔP is the phase difference of the sampling clock C relative to the horizontal synchronizing signal BH. FIG.

FIG. 7 is an explanatory diagram showing the display level of one line of the adjustment-only screen, and shows luminance data D when a screen whose display area is entirely white is stored in the image memory (5) as an adjustment-only screen.
It shows the level of

FIG. 8 is a waveform diagram showing the relationship between the first dot portion in FIG. 7 and the sampling clock C, and shows the sampling clock C based on delay signals R having different delay levels (R=RO to R3).

Next, a conventional sampling phase adjustment method using the video printer shown in FIG. 4 will be described with reference to FIGS. 5 to 8.

Generally, the voltage level of the brightness signal A changes depending on the image as shown in FIG. 6, but since the frequency of the brightness signal A is high, the waveform is dull. Therefore, in order to obtain accurate luminance data D, it is necessary to AD convert the luminance signal A at the center of the dot period. Therefore, it is necessary to adjust the phase of the PLL oscillator (8) that generates the sampling clock C with respect to the phase of the horizontal synchronization signal BH.

Conventionally, when performing such phase adjustment, for example, a luminance signal A is used in which the entire display area is at the maximum luminance level (that is, white).

First, press the adjustment start button (13a) on the operation panel (13).
), the host device (1) generates an image signal ■ in which the entire display screen is white, and the MPU (10) transmits the frequency division ratio (dot frequency/horizontal synchronization) to the PLL oscillator (8). frequency). At this time, the delay signal R from the programmable delay circuit (7) is set to RO, and the phase difference ΔP is, for example, 0.

Based on the sampling clock C obtained in this state, the AD converter (4) performs AD conversion on the luminance signal A, and the input control section (9) stores the luminance data D in the image memory (5).

When the luminance data D for one screen has been captured, the level of the luminance data D between the first dot on the first line and the dot immediately before it (the 11 dot in Fig. 8) is compared, and the luminance difference ΔDo is calculated.
Calculate. At this time, if the waveform dullness is ignored, the level of the first dot is white, and the level of the previous 11 dots is black (no display).

Next, M P U (10) sets a delay value for the programmable delay circuit (7), sets the delay signal R to R1, determines the sampling clock C, and sets the delay signal R to 1 as described above.
Load the brightness data D for the screen into the image memory (5),
The brightness difference ΔD at this time is calculated.

Thereafter, in the same way, while changing the delay value within a range of 1 dot, the delay signal R is set as R2, R3=...,
Each brightness difference ΔDi is calculated sequentially.

Then, the delay value at which the luminance difference ΔDi is maximum is determined as the optimal delay value, and the sampling clock C based on this delay value is
Let the phase difference ΔP be the optimal phase difference.

MPU (10) stores the optimal delay value in non-volatile memory (12) and finishes the phase adjustment operation.

In this way, by loading the experimental white level luminance signal A into the image memory (5) several times, an accurate sampling clock C for converting the luminance signal into luminance data D is automatically set. .

[Problems to be Solved by the Invention] As described above, the conventional sampling phase adjustment method for a video printer is based on a luminance signal A whose entire display area is at a white level.
Is it necessary to generate a normal host mount? If(1
) (normal screen state), there was a problem in that the phase of the sampling clock C could not be adjusted.

The present invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a sampling phase adjustment method for a video printer that can be easily operated even on a general display screen.

[Means for Solving the Problems] A sampling phase adjustment method for a video printer according to the present invention includes the steps of: importing luminance data based on an image signal into an image memory using an initial sampling clock;
A step of extracting, as a reference pixel, a pixel with the largest difference in brightness between adjacent pixels from the brightness data, and a step of importing the brightness data into the image memory while changing the phase difference of the sampling clock with respect to the horizontal synchronization signal included in the image signal. and a step of determining the phase difference with which the luminance difference with respect to the reference pixel is maximum as the optimum phase difference of the sampling clock.

[Operation] In this invention, the screen of the host device in actual use is captured into the image memory, the dot pair with the largest change in brightness is extracted, and the phase difference at which the change in brightness is the largest is determined as the optimum phase difference of the sampling clock. Then, the sampling timing of the luminance signal is determined.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a flowchart diagram showing one embodiment of this invention.
The figure is an explanatory diagram showing a reference pixel in one line of an arbitrary screen, and FIG. 3 is a waveform diagram showing the timing of the sampling clock C for the reference pixel at the maximum luminance level.

The video printer device to which this invention is applied and its basic operation are shown in FIGS. 4 to 6, and M P
It is only necessary that a part of the operation program of U (10) is changed.

Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 4.

First, as described above, when you press the adjustment start button (13a) on the operation panel (13), the MPU (10)
Setting the frequency division ratio for the PLL oscillator (8),
An initial delay value (for example, O) is set in the programmable delay circuit (7).

This creates a PLL oscillator (8
) generates the sampling clock C based on the initial delay signal R (=RO). At this time, the phase difference ΔP between the horizontal synchronization signal BH and the sampling clock C takes an initial value (for example, 0).

In this state, the AD converter (4) outputs the brightness signal A of the initial screen.
is converted into brightness data D, and the input control unit (9) takes in the brightness data D for one screen into the image memory (5) using the initial sampling clock C (step St).

Next, MPU (10) detects the brightness difference ΔD0 between the pixel of interest and the pixel immediately before it from among the brightness data D on the image memory (5), and selects the pixel for which the brightness difference ΔDo is maximum. Extract as a reference pixel <Step S2>.

At this time, for example, as shown in Figure 2, the CRT (
If the character r HJ is displayed on the screen of 2>,
(within a dotted circle with a large luminance change within one line) are extracted as reference pixels.

Next, the luminance data D is taken into the image memory (5) while changing the phase difference ΔP of the sampling clock C with respect to the horizontal synchronization signal BH included in the image signal (step S
3).

That is, M P TJ (10) changes the delay value for the programmable delay circuit (7) and converts the delayed signal R into R1.
, R2, R3, ... (see Figure 3),
Luminance differences ΔD+, ΔD2, ΔD1, etc. regarding the reference pixel
・Measure. At this time, as described above, the delay signal R based on the delay value is changed within one dot period.

Finally, the delay value when the luminance difference ΔDi with respect to the reference pixel is maximum is set as the optimal delay value, and the phase difference ΔP at this time is set as the optimal delay value.
is determined as the optimum phase difference of the sampling clock C (step S4).

That is, the sampling clock C is set at the timing when the change in the luminance level becomes maximum, and the AD conversion timing of the luminance signal A becomes optimal.

The MPU (10) writes the optimal delay value into the non-volatile memory (12) and ends the phase adjustment operation.

Among the above steps S1 to S4, S3 and S4 are the same as the conventional steps.

In this way, the screen of the host device (1) during actual use is captured into the image memory (5), the pair of dots with the maximum brightness change is extracted, and the phase difference ΔP that maximizes this brightness change is determined by the sampling clock C. The sampling timing from the luminance signal A to the luminance data D is determined by setting the optimum phase difference.

Therefore, by capturing an arbitrary luminance signal A several times, the phase of the sampling clock C can be adjusted with a simple and easy operation using the screen in use.

[Effects of the Invention] As described above, according to the present invention, there is a step of loading luminance data based on an image signal into an image memory using an initial sampling clock, and a step of capturing luminance data based on an image signal into an image memory, and selecting a pixel having the maximum luminance difference between adjacent pixels among the luminance data. a step of extracting the luminance data as a reference pixel, a step of importing the luminance data into the image memory while changing the phase difference of the sampling clock with respect to the horizontal synchronization signal included in the image signal, and a step of extracting the luminance data into the image memory while changing the phase difference of the sampling clock with respect to the horizontal synchronization signal included in the image signal, and determining the phase difference with which the luminance difference with respect to the reference pixel is the maximum as the sampling clock. and determining as the optimal phase difference.

Since the sampling timing of the luminance signal is determined using a general screen during actual use of the host device without using a special adjustment screen, a sampling phase adjustment method for video printers that is easy to adjust is created. There are benefits to be gained.

[Brief explanation of the drawing]

FIG. 1 is a flow chart diagram showing an embodiment of the present invention;
FIG. 2 is an explanatory diagram showing an adjustment screen in an embodiment of the present invention, FIG. 3 is a waveform diagram for explaining the operation of step S3 in FIG. 1, and FIG. 4 is a diagram showing a general video printer device. FIG. 5 is an explanatory diagram showing the memory space of the image memory in FIG. Figure 7 is an explanatory diagram showing the adjustment screen in the conventional sampling phase adjustment method;
The figure is a waveform diagram for explaining the phase difference determining step according to the conventional method. (1)...Host outfit! (4)...AD converter (
5)...Image memory (6)...Printing section (7)...
・Programmable delay circuit (8)...PLL oscillator (10)・MPU■...
・Image signal A...Brightness signal D...Brightness data BH...Horizontal synchronization signal C...Sampling clock ΔP...Phase difference Sl...Step S2 to capture the initial screen - Extract the reference pixel Step S3: Capturing the screen by changing the phase difference Step S4: Determining the appropriate phase difference Note that in the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] A step of importing luminance data based on an image signal into an image memory using an initial sampling clock; and a step of extracting a pixel having the maximum luminance difference between adjacent pixels from the luminance data as a reference pixel. , loading the luminance data into the image memory while changing a phase difference of the sampling clock with respect to a horizontal synchronization signal included in the image signal; and determining a phase difference of the sampling clock that maximizes the luminance difference with respect to the reference pixel. A sampling phase adjustment method for a video printer, comprising a step of determining an optimal phase difference.